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Articles 1 - 20 of 20
Full-Text Articles in Engineering
A Model For Rapid Charging Events On International Space Station, Debrup Hui
A Model For Rapid Charging Events On International Space Station, Debrup Hui
Debrup Hui
Surface charging by plasma can be a serious issue for any spacecraft. Though significant charging is not observed in all spacecrafts at all times, it only requires a single episode of extreme charging to result in serious damage. The International Space Station (ISS) is an interesting platform to study these charging effects because of its size and relatively high voltage systems. Of the many kinds of charging observed on ISS, the rapid charging events during solar eclipse exit in a low-density ionosphere is not yet understood. This report is an investigation to understand this phenomenon. This report proposes a simple …
Characterisation Of Large Disturbance Rotor Angle And Voltage Stability In Interconnected Power Networks With Distributed Wind Generation, Lasantha Meegahapola, T Littler
Characterisation Of Large Disturbance Rotor Angle And Voltage Stability In Interconnected Power Networks With Distributed Wind Generation, Lasantha Meegahapola, T Littler
Dr Lasantha G Meegahapola
Wind generation in highly interconnected power networks creates local and centralised stability issues based on their proximity to conventional synchronous generators and load centres. This study examines the large disturbance stability issues (i.e. rotor angle and voltage stability) in power networks with geographically distributed wind resources in the context of a number of dispatch scenarios based on profiles of historical wind generation for a real power network. Stability issues have been analysed using novel stability indices developed from dynamic characteristics of wind generation. The results of this study show that localised stability issues worsen when significant penetration of both conventional …
Capability Constraints To Mitigate Voltage Fluctuations From Dfig Wind Farms When Delivering Ancillary Services To The Network, Lasantha Meegahapola, S Perera
Capability Constraints To Mitigate Voltage Fluctuations From Dfig Wind Farms When Delivering Ancillary Services To The Network, Lasantha Meegahapola, S Perera
Dr Lasantha G Meegahapola
Majority of the wind power resources are typically sited at remote locations in power networks and generated power is transmitted through rural transmission corridors to load centres. With increased penetration level of the wind generation there is an increased requirement to provide ancillary services from distributed wind power resources, hence they are operated under different control strategies to provide ancillary services to the network. The control strategies and capability characteristics will significant impact on voltage fluctuations in distribution networks. This paper presents a comparative analysis between different wind generator control strategies (i.e. power factor control strategy, voltage control strategy and …
Refractory Plasmonics With Titanium Nitride: Broadband Metamaterial Absorber, W Li, U. Guler, N. Kinsey, G. Naik, A. Boltasseva, J. Guan, V Shalaev, A. Kildishev
Refractory Plasmonics With Titanium Nitride: Broadband Metamaterial Absorber, W Li, U. Guler, N. Kinsey, G. Naik, A. Boltasseva, J. Guan, V Shalaev, A. Kildishev
U. Guler
A high-temperature stable broadband plasmonic absorber is designed, fabricated, and optically characterized. A broadband absorber with an average high absorption of 95% and a total thickness of 240 nm is fabricated, using a refractory plasmonic material, titanium nitride. This absorber integrates both the plasmonic resonances and the dielectric-like loss. It opens a path for the interesting applications such as solar thermophotovoltaics and optical circuits.
Non-Linear Collision Analysis, Thomas Eisenbarth, Xin Ye, Cong Chen
Non-Linear Collision Analysis, Thomas Eisenbarth, Xin Ye, Cong Chen
Thomas Eisenbarth
As an unsolved issue for embedded crypto solutions, side channel attacks are challenging the security of the Internet of things. Due to the advancement of chip technology, the nature of side channel leakage becomes hard to characterize with a fixed leakage model. In this work, a new non-linear collision attack is proposed in the pursuit of the side channel distinguishers with minimal assumption of leakage behavior. The attack relies on a weaker assumption than classical DPA: it does not require a specific leakage model. The mechanism of collision generation enables independent recovery of partial keys so that for the first …
Suboptimal Mppt Control For Power Management In Pv-Diesel Remote Area Power Supply Systems, Lasantha Meegahapola, Y J Tan, K M Muttaqi
Suboptimal Mppt Control For Power Management In Pv-Diesel Remote Area Power Supply Systems, Lasantha Meegahapola, Y J Tan, K M Muttaqi
Dr Lasantha G Meegahapola
Maximum power point tracking (MPPT) is commonly being used in solar-photovoltaic (PV) power generation systems to maximise solar energy extraction. In this paper it is proposed to operate the solar-PV system at the suboptimal MPPT to manage power balance in a remote area power supply (RAPS) system. This is performed based on three different operating modes: 1) Frequency control mode; 2) Active power control mode; 3) MPPT control mode. The operating modes are decided based on the load level and the operating mode of the diesel generator (i.e. synchronous condenser mode or generator mode). This power management strategy balances the …
Dispatch Strategy To Minimise Uncertainty In Wind Power Generation In The Australian National Electricity Market, Lasantha Meegahapola, Amila Wickramasinghe, A P Agalgaonkar, S Perera
Dispatch Strategy To Minimise Uncertainty In Wind Power Generation In The Australian National Electricity Market, Lasantha Meegahapola, Amila Wickramasinghe, A P Agalgaonkar, S Perera
Dr Lasantha G Meegahapola
With increased penetration of wind power, scheduling generators to meet the forecast demand of a power system is becoming an increasingly challenging task for the system operators. Uncertainty associated with the generation expected from wind plants adds to the load demand uncertainty, making it necessary to retain additional reserves to maintain the balance between demand and supply of power. In the Australian national electricity market (NEM), sophisticated wind forecasting techniques are employed to reduce the uncertainty in wind generation. Despite being able to project the contribution of wind power to a reasonable accuracy, wind power plants are currently not considered …
Characterization Of Gas Turbine Lean Blowout During Frequency Excursions In Power Networks, Lasantha Meegahapola, D Flynn
Characterization Of Gas Turbine Lean Blowout During Frequency Excursions In Power Networks, Lasantha Meegahapola, D Flynn
Dr Lasantha G Meegahapola
While gas turbines are popular in power networks due to reduced emissions and economical operation, their frequency response characteristics are substantially different from other conventional generation technologies; hence, gas turbine dynamics may influence system stability during significant frequency excursions. This study characterizes the impact of gas turbine combustor lean blowout (LBO) while considering large frequency excursions and, in particular, during short-circuit faults. Studies have shown that combined-cycle gas turbines are more vulnerable to an LBO condition during short-circuit events when they operate at rated power output. A sensitivity analysis was also carried out against a number of factors influencing the …
Forecasting Natural Gas Demand: The Role Of Physical And Economic Factors, Ronald Brown, David Clark, George Corliss, Farrokh Nourzad, Thomas Quinn, Catherine Twetten
Forecasting Natural Gas Demand: The Role Of Physical And Economic Factors, Ronald Brown, David Clark, George Corliss, Farrokh Nourzad, Thomas Quinn, Catherine Twetten
George F Corliss
No abstract provided.
A Reservation-Based Extended Transaction Protocol For Coordination Of Web Services, Wenbing Zhao, Firat Kart, Louise Moser, P. Melliar-Smith
A Reservation-Based Extended Transaction Protocol For Coordination Of Web Services, Wenbing Zhao, Firat Kart, Louise Moser, P. Melliar-Smith
Wenbing Zhao
Web services can be used to automate business activities that span multiple enterprises over the Internet. Such business activities require a coordination protocol to reach consistent results among the participants in the business activity. In the current state of the art, either classical distributed transactions or extended transactions with compensating transactions are used. However, classical distributed transactions lock data in the databases of different enterprises for unacceptable durations or involve repeated retries, and compensating transactions can lead to inconsistencies in the databases of the different enterprises. In this article, we describe a novel reservation protocol that can be used to …
Design Considerations For Inertia Emulating Controllers Used In Variable Speed Wind Turbines, Lasantha Meegahapola, Amila Wickramasinghe, A P Agalgaonkar, S Perera
Design Considerations For Inertia Emulating Controllers Used In Variable Speed Wind Turbines, Lasantha Meegahapola, Amila Wickramasinghe, A P Agalgaonkar, S Perera
Dr Lasantha G Meegahapola
High penetration of wind power into power systems is likely to cause difficulties in maintaining system frequency, as in contrast to conventional synchronous generators, variable speed wind turbines (VSWTs) do not directly contribute to system inertia. To overcome this issue, it has been proposed to emulate inertia by VSWTs by extracting the kinetic energy of the turbine rotor. However, proper designing of the inertia emulating controller is essential for the optimal use of the energy potential and safe operation of the wind turbine. Some of the common controller concepts used for inertia emulation have inherent weaknesses, limiting the frequency support …
Voltage Unbalance Emission Allocation Using Constrained Bus Voltage Method In Radial Distribution Networks, Lasantha Meegahapola, D Perera, S Perera, P Ciufo
Voltage Unbalance Emission Allocation Using Constrained Bus Voltage Method In Radial Distribution Networks, Lasantha Meegahapola, D Perera, S Perera, P Ciufo
Dr Lasantha G Meegahapola
The International Electrotechnical Committee Technical Report IEC 61000-3-13 is focused on the coordination of voltage unbalance (VU) in power systems by prescribing a methodology to determine individual VU emission allocation limits to installations. This paper provides an alternative VU emission allocation process to that of the IEC Technical Report, which is based on the concept of constrained bus voltage (CBV) method. The proposed methodology can be used in relation to radial distribution networks with symmetrical distribution lines. Several application examples of the proposed methodology are presented. It is shown that the proposed methodology is superior in comparison to the VU …
Characterisation Of Gas Turbine Dynamics During Frequency Excursions In Power Networks, Lasantha Meegahapola
Characterisation Of Gas Turbine Dynamics During Frequency Excursions In Power Networks, Lasantha Meegahapola
Dr Lasantha G Meegahapola
Gas turbines inherently depict unique frequency response characteristics compared with other conventional synchronous generation technologies as their active power output is not entirely determined by the governor response during frequency deviations of the power network. Thus, gas turbine dynamics significantly influence on system stability during frequency events in power networks. Power system and power plant operators require improved understanding of the gas turbine characteristics during various frequency events in order to mitigate adverse impact on power system. Therefore a comparative analysis has been performed between combined-cycle gas turbines (CCGTs) and open-cycle gas turbines (OCGTs) in order to characterise the dynamic …
Capability Chart: A New Tool For Grid-Tied Microgrid Operation, Lasantha Meegahapola, A Jayawardena, Duane Robinson, S Perera
Capability Chart: A New Tool For Grid-Tied Microgrid Operation, Lasantha Meegahapola, A Jayawardena, Duane Robinson, S Perera
Dr Lasantha G Meegahapola
Increasing penetration of distributed resources have enabled the development of the microgrid concept. Similar to traditional generators, microgrids can participate in the energy market to achieve technical, economical and environmental benefits. In order to facilitate the participation in energy markets, microgrid operators need to be aware of the full capability of the microgrids. This paper presents a systematic approach for developing a capability chart for a grid-tied microgrid which represents the active and reactive power capability at the grid supply point. Capability charts have been developed for two different microgrids and the impacts of different modelling aspects have been analysed …
A Review Of Parallel Operation Of Active Power Filters In The Distributed Generation System, Shafiuzzaman Khadem, Malabika Basu, Michael Conlon
A Review Of Parallel Operation Of Active Power Filters In The Distributed Generation System, Shafiuzzaman Khadem, Malabika Basu, Michael Conlon
Dr. Shafiuzzaman Khan Khadem
In this paper a technical review of parallel operation of Active Power Filter (APF) for harmonic power compensation in distributed generation (DG) network has been presented. Controlling methods and connection topologies with their pros and cons are described. Recent improvements in controlling and future trends for the application of APFs in distributed mode are also identified.
Power Quality Improvement Of Distributed Generation Integrated Network With Unified Power Quality Conditioner., Shafiuzzaman Khan Khadem
Power Quality Improvement Of Distributed Generation Integrated Network With Unified Power Quality Conditioner., Shafiuzzaman Khan Khadem
Dr. Shafiuzzaman Khan Khadem
With the increased penetration of small scale renewable energy sources in the electrical distribution network, maintenance or improvement of power quality has become more critical than ever where the level of voltage and current harmonics or disturbances can vary widely. For this reason, Custom Power Devices (CPDs) such as the Unified Power Quality Conditioner (UPQC) can be the most appropriate solution for enhancing the dynamic performance of the distribution network, where accurate prior knowledge may not be available. Therefore, the main objective of the present research is to investigate the (i) placement (ii) integration (iii) capacity enhancement and (iv) real …
Microgrids Of Commercial Buildings: Strategies To Manage Mode Transfer From Grid Connected To Islanded Mode, Lasantha Meegahapola, D Robinson, A Agalgaonkar, S Perera, P Ciufo
Microgrids Of Commercial Buildings: Strategies To Manage Mode Transfer From Grid Connected To Islanded Mode, Lasantha Meegahapola, D Robinson, A Agalgaonkar, S Perera, P Ciufo
Dr Lasantha G Meegahapola
Microgrid systems located within commercial premises are becoming increasingly popular and their dynamic behavior is still uncharted territory in modern power networks. Improved understanding in design and operation is required for the electricity utility and building services design sectors. This paper evaluates the design requirements for a commercial building microgrid system to facilitate seamless mode transition considering an actual commercial building microgrid system. A dynamic simulation model of the proposed microgrid system is established (utilizing DIgSILENT Power Factory) to aid the development of planning and operational philosophy for the practical system. An economic operational criterion is developed for the microgrid …
Robust Stability, Constrained Stabilization, And Observer-Based Controller Designs For Time Delay Systems, Hanai Sadaka
Robust Stability, Constrained Stabilization, And Observer-Based Controller Designs For Time Delay Systems, Hanai Sadaka
Hanai Sadaka
This thesis initially presents the problem of stability pertaining to delay systems and provides useful results on stability analysis using linear matrix inequalities (LMIs). The connection between recently published results on stability robustness in the domain of time delays and robust stability with respect to structured perturbation of system matrices is investigated. Consequently, computable stability radius formulas for multi-delay systems using Rekasius substitution are derived. Using the concepts of kernel and offspring curves, which describe the complete portrait of possible imaginary characteristic roots of the nominal system, the fundamental stability region is defined among a set of disjoint stability regions …
Privacy Protection Framework With Defined Policies For Service-Oriented Architecture, David Allison, Miriam Capretz, Hany Elyamany, Shuying Wang
Privacy Protection Framework With Defined Policies For Service-Oriented Architecture, David Allison, Miriam Capretz, Hany Elyamany, Shuying Wang
David S Allison
Service-Oriented Architecture (SOA) is a computer systems design concept which aims to achieve reusability and integration in a distributed environment through the use of autonomous, loosely coupled, interoperable abstractions known as services. In order to interoperate, communication between services is very important due to their autonomous nature. This communication provides services with their functional strengths, but also creates the opportunity for the loss of privacy. In this paper, a Privacy Protection Framework for Service-Oriented Architecture (PPFSOA) is described. In this framework, a Privacy Service (PS) is used in combination with privacy policies to create privacy contracts that outline what can …
The Sky Is The Limit, Alexander Hayes
The Sky Is The Limit, Alexander Hayes
Alexander Hayes Mr.
IEEE Technology and Society Magazine Associate Editor Alexander Hayes interviewed Glass Explorer Cecilia Abadie on January 21, 2013. The complete Google Hangout interview is available for viewing on YouTube at http://goo.gl/YFFbxJ.